ABSTRACT
In the 1940s, Dr. Leo Kanner described 11 children with “autistic disturbances of affective contact,” and even today, that characterization continues to form the basis of the diagnostic criteria for autistic disorder (1). Epidemiological studies describing the prevalence and risk factors for autistic disorder and autism spectrum disorders (ASDs) did not appear in the scientific literature until the late 1960s and early 1970s (2-4). Since these earlier investigations, several population-based prevalence studies have been conducted. However, these vary 5 in terms of their methods, case definitions, and population size; hence, comparisons of estimates from these studies are difficult. Other factors contributing to the lack of epidemiological understanding of autism stem from the paucity of well-designed studies that are able to examine trends over time, as well as a range of risk factors, both biological and sociodemographic, for autism.
